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Q: Has CO2 Ever Caused a Natural Disaster?

Carbon dioxide produced by volcanoes leaks into the water and accumulates in high concentrations at the bottom of three deep lakes in western Africa. Natural disasters have occured at two of them.

In 1986, some disturbance caused the carbon dioxide from the bottom of Lake Nyos in Cameroon to rise to the surface. The disturbance is still unknown, but scientists now believe it could have been a landslide, localized heating, wave action, or a process called limnetic eruption in which carbon dioxide bubbles spontaneously from saturated water. As the carbon dioxide rose, the pressure decreased and the carbon dioxide formed gas bubbles. A cloud of carbon dioxide escaped from the lake. The high concentrations killed livestock and people.

In 1984, a similar event occured at another deep lake, Lake Monoun in Cameroon, but with much smaller loss of life. A third deep lake on the border of Rwanda and the Democratic Republic of Congo, called Lake Kivu, also accumulates gases including carbon dioxide at depth, but has remained stable.

Since the time of the disasters, scientists from France and Cameroon have collaborated to install degassing devices in Lakes Nyos and Monoun to help prevent carbon dioxide from accumulating in the deep water.

Image from http://www.geo.arizona.edu

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A: Yes. Nature does not have regulations or safeguards like carbon sequestration sites do.

Storage sites are chosen so that they are not escape points for carbon dioxide, like volcanoes are. A volcano is a flaw in the earth, like a pimple, that allows gases to escape. CO2 storage sites are chosen with the opposite types of geological characteristics, ones that stop carbon dioxide from leaking.

A geologic storage reservoir is not an open space like a cave or a balloon. It is porous rock saturated with saltwater. The carbon dioxide disperses in the spaces between the grains of the rock, and it dissolves in the water. Dense rock layers above the reservoir hold the carbon dioxide in the reservoir, providing another layer of security.

Sequestration sites are regulated under the Underground Injection Control Program. Mandated monitoring tells site operators when it is okay to continue injecting and, in the case of a leak, when to stop.

None of these safeguards, neither the redundant containment mechanisms of the reservoir nor the monitoring, were in place at Lake Nyos or Lake Monoun at the time of the disasters. These safeguards are required for any geological sequestration project.

Image from http://www.geo.arizona.edu

To read an article in EOS, a newspaper published by the American Geophysical Union, that discusses more about how scientists engineered the safeguards now installed at Lakes Nyos and Monoun, click on the icon to the left.

For an update on progress degassing Lakes Nyos and Monoun, as well as efforts to use the retrieved methane for power, click the icon to the left.

In Mammoth Lakes, California, carbon dioxide seeping into the soil from volcanic activity has killed trees by displacing oxygen from their roots. For more discussion of this phenomena, click on the icon at the left.

The soil beneath Ciampino, near Rome, Italy, is charged with unnaturally high concentrations of carbon dioxide from volcanic activity. No fatalities or other ill effects have occurred and people living in the area have developed mechanisms for living with the risk. The icon at the left links to a study risks from CO2 near Ciampino.